JP2013112572A - Hydrogen occlusion method, and hydrogen occluding material - Google Patents

Hydrogen occlusion method, and hydrogen occluding material Download PDF

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JP2013112572A
JP2013112572A JP2011261064A JP2011261064A JP2013112572A JP 2013112572 A JP2013112572 A JP 2013112572A JP 2011261064 A JP2011261064 A JP 2011261064A JP 2011261064 A JP2011261064 A JP 2011261064A JP 2013112572 A JP2013112572 A JP 2013112572A
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hydrogen
porous carbon
hydrogen storage
carbon
alkali
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Hidetoshi Saito
秀俊 斎藤
Daiki Akasaka
大樹 赤坂
Shigeo Oshio
茂夫 大塩
Yasutami Toda
育民 戸田
Yoshinori Tsuda
欣範 津田
Yoshihisa Tanaka
好久 田中
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FUSE TECHNONET KK
Nagaoka University of Technology NUC
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FUSE TECHNONET KK
Nagaoka University of Technology NUC
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/32Hydrogen storage

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Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen occlusion technique capable of achieving a high density of hydrogen occluded per volume or mass and ensuring easy handling in storage and transportation of hydrogen.SOLUTION: The hydrogen occlusion method includes: a step (S1) of subjecting a carbon material to carbonization; a step (S2) of subjecting the resultant carbon material to alkali activation; a step (S3) of housing a porous carbon produced by the alkali activation step into a vessel; and a step (S4) of introducing hydrogen into the vessel so that an equilibrium pressure reaches 0.5 to 20 MPa, while keeping the interior of the vessel at a temperature within the range of 77 to 150 K. The porous carbon including a plurality of micro pores and a plurality of meso pores, wherein a specific surface area of the porous carbon as a whole is 700 to 3,800 m/g, and the meso pores possess pore diameters in the range of 2 to 10 nm, is used as the porous carbon subjected to carbonization and activation adjustment.

Description

本発明は、炭素材料を用いた水素吸蔵方法及び水素吸蔵材料に関するものである。   The present invention relates to a hydrogen storage method using a carbon material and a hydrogen storage material.

昨今、石油資源の枯渇化と化石燃料による環境問題が懸念され、石油に代替する新たなエネルギー源の開発が喫緊の課題となっている。このエネルギー源の代替候補として、水素が注目されている。水素は燃焼生成物が水であるため、環境破壊の心配が無いクリーンなエネルギーである。   In recent years, there is concern about the depletion of petroleum resources and the environmental problems caused by fossil fuels, and the development of new energy sources to replace oil has become an urgent issue. Hydrogen is attracting attention as an alternative candidate for this energy source. Hydrogen is clean energy with no fear of environmental destruction because the combustion product is water.

この水素エネルギーを実際に利用していくには、水素を有効に吸蔵、貯蔵、運搬する技術の確立が必要不可欠となる。現在、水素を輸送、貯蔵する技術としては、高圧ガス、液化水素、水素貯蔵合金、水素吸蔵材料などが提案されている(非特許文献1)。   In order to actually use this hydrogen energy, it is indispensable to establish technology for effectively storing, storing and transporting hydrogen. Currently, high-pressure gas, liquefied hydrogen, hydrogen storage alloys, hydrogen storage materials, and the like have been proposed as technologies for transporting and storing hydrogen (Non-patent Document 1).

このうち特に、水素吸蔵材料を用いた技術は、水素の放出が常温で可能であるのでシステムが簡素である上、一般に水素放出時に熱を必要とせずエネルギー効率が高いなどの特徴があるため、有望視され、その材料の開発が盛んになされている。現在までに、カーボンナノチューブやカーボンナノファイバーなどの細孔炭素系材料が高い吸蔵量を示すとの報告(非特許文献2)があるが、再現性が疑問視されており、十分な再現性を持ちながら高い吸蔵性能を持つ水素吸蔵材料あるいは水素凝集材料の開発は未だ実現したとは言えない状況である。   Among these, in particular, the technology using a hydrogen storage material is characterized in that the release of hydrogen is possible at room temperature, so the system is simple, and generally it does not require heat when releasing hydrogen and is highly energy efficient. The material is promising and the development of the material is actively made. To date, there is a report (Non-Patent Document 2) that porous carbon-based materials such as carbon nanotubes and carbon nanofibers show high occlusion, but reproducibility has been questioned and sufficient reproducibility has been achieved. The development of a hydrogen storage material or a hydrogen agglomeration material that has high storage performance while being held has not yet been realized.

また、有機物を焼成して得られる炭素質を、水蒸気や二酸化炭素と反応させ、その細孔構造を発達させた多孔質炭素も水素吸蔵媒体として報告されている(非特許文献3〜5)。これらの従来の報告によれば、高い水素吸蔵能にはミクロポーラスな多孔質炭素の持つ高い比表面積が必要であり、水素吸蔵量を増大させるにはミクロ孔が必要であることを示している。特に、非特許文献4では、約0.6nmの細孔が常温において水素吸蔵に適していると報告されている。   In addition, porous carbon obtained by reacting a carbonaceous material obtained by firing an organic substance with water vapor or carbon dioxide and developing its pore structure has been reported as a hydrogen storage medium (Non-Patent Documents 3 to 5). These previous reports indicate that high hydrogen storage capacity requires high specific surface area of microporous porous carbon, and micropores are required to increase hydrogen storage capacity. . In particular, Non-Patent Document 4 reports that pores of about 0.6 nm are suitable for hydrogen storage at room temperature.

また、本発明者らは、この水素吸蔵材料を用いた技術について研究を重ね、例えば、特許文献1において、多孔質炭素内に配置された水素の周囲温度が水素液化温度(20.3K)より高くかつ気化状態と通常みなされる温度範囲であっても、水素液化温度に近い所定の温度域(77〜150K)では、水素は液化水素が行う凝縮と同様な吸蔵挙動を示すことを利用した水素吸蔵方法や水素吸蔵装置を提案し、1.6〜4.0wt.%程度の水素吸蔵量を達成可能であることを報告している。なお、この特許文献1に開示の水素吸蔵用炭素材料には、多数のミクロ孔によって形成された多孔質体(全比表面積に占めるミクロ孔による比表面積の割合が非常に高い多孔質体)を採用している。   In addition, the present inventors have conducted research on the technology using this hydrogen storage material. For example, in Patent Document 1, the ambient temperature of hydrogen arranged in porous carbon is higher than the hydrogen liquefaction temperature (20.3 K). Hydrogen utilizing the fact that hydrogen exhibits a storage behavior similar to the condensation performed by liquefied hydrogen in a predetermined temperature range (77 to 150 K) close to the hydrogen liquefaction temperature even in a high temperature range that is normally regarded as a vaporized state. A storage method and a hydrogen storage device are proposed, and 1.6 to 4.0 wt. It has been reported that hydrogen storage capacity of about% can be achieved. In addition, in the carbon material for hydrogen storage disclosed in Patent Document 1, a porous body formed by a large number of micropores (a porous body having a very high specific surface area ratio by micropores in the total specific surface area) is used. Adopted.

しかしながら、水素吸蔵技術の高性能化への市場の要求は益々高まっており、特許文献1に開示の水素吸蔵技術でさえも、水素吸蔵特性の観点において更に改善の余地がある。   However, the market demand for higher performance of the hydrogen storage technology is increasing, and even the hydrogen storage technology disclosed in Patent Document 1 has room for further improvement in terms of hydrogen storage characteristics.

特開2011−057457号公報JP 2011-057457 A

大角泰章 編、「水素吸蔵合金‐その物性と応用‐」、アグネ技術センター、1993年Edited by Yasuaki Osaku, "Hydrogen Storage Alloys-Their Properties and Applications", Agne Technology Center, 1993 エー・チャンバース(A. Chambers)他,ジャーナル・オブ・フィジカル・ケミストリー(J. Phys. Chem.),(米国),B102巻,1998年,p.4253−4256A. Chambers et al., Journal of Physical Chemistry (J. Phys. Chem.), (USA), B102, 1998, p. 4253-4256 ヨシツグ・コジマ(Yoshitsugu. Kojima)他, ジャーナル・オブ・アロイ・アンド・コンパウンズ(J. Alloys Comp.), 421巻, 1−2号,p.204−208 (2006)Yoshishitu. Kojima et al., Journal of Alloy and Compounds, 421, 1-2, p. 204-208 (2006) エー・トォウジィク(A. Touzik),エイチ・ハーマン(H. Hermann),ケミカル・フィジックス・レターズ(Chem. Phys. Lett.), 416, 137 (2005)A. Touzik, H. Hermann, Chem. Phys. Letters, 416, 137 (2005) イー・ディビッド(E. David), ジャーナル・オブ・マテリアルズ・プロセシング・テクノロジー(J. Mater. Proc. Tech.), 169, 162 (2005).E. David, Journal of Materials Processing Technology (J. Mater. Proc. Tech.), 169, 162 (2005).

本発明は、以上の状況に鑑みてなされたものであり、その目的は、体積又は質量当たりに吸蔵できる水素密度が高く、貯蔵・輸送上の取扱が容易な水素吸蔵技術を提供することである。   The present invention has been made in view of the above situation, and an object of the present invention is to provide a hydrogen storage technology that has a high hydrogen density that can be stored per volume or mass and is easy to handle in storage and transportation. .

本願の発明者らは、鋭意検討の末、多孔質炭素材料の水素凝集サイトはミクロ孔のみであるとの従来の知見を覆し、ミクロ孔より大きな寸法のメゾ孔にも水素が凝集可能であることを見出し、本発明を完成させるに至った。   The inventors of the present application, after intensive studies, overturn the conventional knowledge that the hydrogen aggregation sites of the porous carbon material are only micropores, and hydrogen can also aggregate into mesopores with dimensions larger than the micropores. As a result, the present invention has been completed.

すなわち、本発明は、次の構成又は特徴を有するものである。
(態様1)
炭素材料に炭化を施す工程と、
前記炭化工程により処理された前記炭素材料にアルカリ賦活を施す工程と、
前記アルカリ賦活工程により作製された多孔質炭素を容器内に収容する工程と、
前記容器内部を77K〜150Kの範囲内の温度に保持しながら、平衡状態圧力が0.5MPa〜20MPaになるように水素を該容器内部に導入する工程と、を含み、かつ、
前記多孔質炭素として、複数のミクロ孔と複数のメゾ孔とを含み、前記多孔質炭素の全体の比表面積が700m/g〜3800m/gであり、かつ、該メゾ孔は、2nm〜10nmの範囲の孔径を有する多孔質炭素を使用することを特徴とする水素吸蔵方法。
(態様2)
前記炭化工程では、前記炭素材料に籾殻を使用し、かつ、前記炭素材料を燃焼窯内で回転させながら加熱する工程を含むことを特徴とする態様1に記載の水素吸蔵方法。
(態様3)
前記アルカリ賦活工程では、前記炭素材料との重量比で3倍〜8倍のアルカリ賦活剤を添加することを特徴とする態様1又は2に記載の水素吸蔵方法。
(態様4)
前記アルカリ賦活剤として、水酸化カリウム、水酸化ナトリウム、水酸化リチウム、炭酸カリウム、炭酸ナトリウムの少なくとも1つを使用することを特徴とする態様3に記載の水素吸蔵方法。
(態様5)
前記アルカリ賦活工程では、前記アルカリ賦活剤を使用して賦活工程を行った後に、先の前記賦活工程の該アルカリ賦活剤と異なる種類の前記アルカリ賦活剤を使用して賦活工程を複数回行うことを特徴とする態様3又は4に記載の水素吸蔵方法。
(態様6)
前記多孔質炭素として、前記ミクロ孔が占めるミクロ孔容積に対して前記メゾ孔が占めるメゾ孔容積の比率が0.5以上になる多孔質炭素を使用することを特徴とする態様1〜5のいずれかに記載の水素吸蔵方法。
(態様7)
複数のミクロ孔と複数のメゾ孔とを含んだ多孔質炭素からなり、
前記多孔質炭素の全体の比表面積が700m/g〜3800m/gであり、かつ、
該メゾ孔は、2nm〜10nmの範囲の孔径を有することを特徴とする水素吸蔵材料。
(態様8)
前記多孔質炭素は籾殻を炭化処理した後にアルカリ賦活処理を施したものであり、かつ、
前記ミクロ孔が占めるミクロ孔容積に対して前記メゾ孔が占めるメゾ孔容積の比率が0.5以上に設定されたものであることを特徴とする態様7に記載の水素吸蔵材料。
That is, the present invention has the following configuration or characteristics.
(Aspect 1)
A step of carbonizing the carbon material;
Applying alkali activation to the carbon material treated by the carbonization step;
Storing the porous carbon produced by the alkali activation step in a container;
Introducing hydrogen into the container so that the equilibrium pressure is 0.5 MPa to 20 MPa while maintaining the inside of the container at a temperature in the range of 77 K to 150 K, and
Examples porous carbon, and a plurality of micropores and a plurality of mesopores, the total specific surface area of the porous carbon is 700m 2 / g~3800m 2 / g, and the meso pores, 2 nm to A method for storing hydrogen, characterized by using porous carbon having a pore size in the range of 10 nm.
(Aspect 2)
The hydrogen storage method according to aspect 1, wherein the carbonizing step includes a step of using rice husk as the carbon material and heating the carbon material while rotating in a combustion kiln.
(Aspect 3)
3. The hydrogen storage method according to aspect 1 or 2, wherein, in the alkali activation step, an alkali activator of 3 to 8 times in weight ratio to the carbon material is added.
(Aspect 4)
The hydrogen storage method according to aspect 3, wherein at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium carbonate, and sodium carbonate is used as the alkali activator.
(Aspect 5)
In the alkali activation step, after the activation step is performed using the alkali activation agent, the activation step is performed a plurality of times using the alkali activation agent of a different type from the alkali activation agent in the previous activation step. 5. The hydrogen storage method according to aspect 3 or 4, wherein
(Aspect 6)
The porous carbon having a ratio of the mesopore volume occupied by the mesopores to the micropore volume occupied by the micropores is 0.5 or more as the porous carbon. The hydrogen storage method according to any one of the above.
(Aspect 7)
It consists of porous carbon containing multiple micropores and multiple mesopores,
The total specific surface area of the porous carbon is 700m 2 / g~3800m 2 / g, and,
The mesopores have a pore diameter in the range of 2 nm to 10 nm.
(Aspect 8)
The porous carbon has been subjected to an alkali activation treatment after carbonizing the rice husk, and
8. The hydrogen storage material according to aspect 7, wherein the ratio of the mesopore volume occupied by the mesopores to the micropore volume occupied by the micropores is set to 0.5 or more.

以上のような構成をなす本発明は、次のような顕著な効果を奏する。   The present invention configured as described above has the following remarkable effects.

本発明の水素吸蔵方法によれば、その方法での炭化処理工程とアルカリ賦活処理工程を実施することで、例えば、2060m/gを超える非常に高い比表面積を有した水素吸蔵材料を作製及び使用することが可能である。 According to the hydrogen storage method of the present invention, by performing the carbonization treatment step and the alkali activation treatment step in the method, for example, a hydrogen storage material having a very high specific surface area exceeding 2060 m 2 / g is produced and It is possible to use.

また、本発明の水素吸蔵方法によれば、従来重要視されていた2nm未満のミクロ孔が占める容積に対して、本発明者らが注目した2nm以上のメゾ孔が占める容積の割合を増加させた水素吸蔵材料を作製することができる。   In addition, according to the hydrogen storage method of the present invention, the ratio of the volume occupied by mesopores of 2 nm or more noted by the present inventors to the volume occupied by micropores of less than 2 nm, which has been regarded as important in the past, is increased. A hydrogen storage material can be produced.

この水素吸蔵材料は、ミクロ孔のみならずメゾ孔も水素吸蔵サイトになり得ることから、水素を液化温度まで冷却しない環境温度(例えば、77K)でも、現時点において水素の平衡圧力が10MPa(つまり、約100気圧)の下で9wt.%の最大水素吸蔵量を発揮することが可能である。
例えば、9wt.%の水素吸蔵特性を示す活性炭を燃料タンク(例えば、50Lタンク)に詰めた仮定すると、このタンクには25kgの活性炭を収容できる。そうすると、このタンク内の25kg分の活性炭に吸蔵可能な水素は、100気圧の圧力下で2.25kg(=25×0.09)であると試算される。一方、従来の水素の充填方法、例えば、常温(298K)下で同量(2.25kg)の水素を50L用高圧ボンベへそのまま充填することを仮定すると、理想気体の状態方程式に依れば、約550気圧という非常に高い圧力が必要となる。
要するに、本発明の水素吸蔵方法によれば、本発明の水素吸蔵材料に液体に近い状態で水素が貯蔵され、かつ、圧力に寄与する気体状態の水素が減少するため、水素タンクの圧力を低くし、かつ、多くの水素を貯蔵することが可能となる。
In this hydrogen storage material, not only micropores but also mesopores can become hydrogen storage sites, so even at an environmental temperature (for example, 77 K) where hydrogen is not cooled to the liquefaction temperature, the hydrogen equilibrium pressure is 10 MPa (that is, 9 wt. % Of the maximum hydrogen storage capacity.
For example, 9 wt. Assuming that activated carbon showing% hydrogen storage characteristics is packed in a fuel tank (for example, 50 L tank), this tank can accommodate 25 kg of activated carbon. Then, hydrogen that can be stored in 25 kg of activated carbon in the tank is estimated to be 2.25 kg (= 25 × 0.09) under a pressure of 100 atm. On the other hand, assuming that the same amount (2.25 kg) of hydrogen is charged into a 50 L high-pressure cylinder as it is under a conventional hydrogen filling method, for example, at room temperature (298 K), according to the equation of state of an ideal gas, A very high pressure of about 550 atmospheres is required.
In short, according to the hydrogen storage method of the present invention, hydrogen is stored in a state close to a liquid in the hydrogen storage material of the present invention, and gaseous hydrogen contributing to the pressure decreases, so the pressure of the hydrogen tank is reduced. In addition, a large amount of hydrogen can be stored.

本発明に係る水素吸蔵方法の各工程を示したフローチャートである。It is the flowchart which showed each process of the hydrogen storage method which concerns on this invention. 特に好ましい態様の炭化処理工程を説明した図である。It is a figure explaining the carbonization process process of the especially preferable aspect. 特に好ましい態様のアルカリ賦活処理工程を説明した図である。It is a figure explaining the alkali activation process of the especially preferable aspect. 本発明によって作製された多孔質炭素のミクロ孔の分布を示した図である。It is the figure which showed distribution of the micropore of the porous carbon produced by this invention. 本発明によって作製された多孔質炭素のメゾ孔の分布を示した図である。It is the figure which showed distribution of the mesopores of the porous carbon produced by this invention. 水素吸蔵特性評価装置の概略を示した図である。It is the figure which showed the outline of the hydrogen storage characteristic evaluation apparatus. 本発明によって作製された多孔質炭素の水素吸蔵特性(水素平衡圧力と水素吸蔵量との関係)を示した図である。It is the figure which showed the hydrogen storage characteristic (relationship between hydrogen equilibrium pressure and hydrogen storage amount) of the porous carbon produced by this invention. BET比表面積と最大水素吸蔵量との関係を示した図である。It is the figure which showed the relationship between a BET specific surface area and the maximum hydrogen occlusion amount. ミクロ孔容積と最大水素吸蔵量との関係を示した図である。It is the figure which showed the relationship between a micropore volume and the maximum hydrogen occlusion amount. ミクロ孔容積と水素吸蔵密度との関係、又はメゾ孔容積と水素吸蔵密度との関係を示した図である。It is the figure which showed the relationship between a micropore volume and hydrogen storage density, or the relationship between a mesopore volume and hydrogen storage density. 容積比と水素吸蔵密度との関係を示した図である。It is the figure which showed the relationship between volume ratio and hydrogen storage density.

以下、本発明を図面に示す実施の形態に基づき説明するが、本発明は、下記の具体的な実施形態に何等限定されるものではない。   Hereinafter, although the present invention is explained based on an embodiment shown in a drawing, the present invention is not limited to the following concrete embodiment at all.

(水素吸蔵方法)
先ず、炭素材料を多孔質化して水素を吸蔵させる水素吸蔵方法について詳しく説明する。図1は、本発明に係る水素吸蔵方法の各工程S1〜S4を示したフローチャートである。
(Hydrogen storage method)
First, a hydrogen storage method for making a carbon material porous and storing hydrogen will be described in detail. FIG. 1 is a flowchart showing steps S1 to S4 of the hydrogen storage method according to the present invention.

(炭化処理)
先ず、図1に示すように、炭素材料に炭化処理を施す(工程S1)。ここで、「炭化処理」とは、加熱によって炭素材料中の有機物質を分解して、炭素に富んだ状態にさせることを意味する。炭素材料を加熱させる手段として、燃焼装置、過熱水蒸気焼成装置、電気炉などが挙げられるが、必ずしもこれらに限定されない。
(Carbonization treatment)
First, as shown in FIG. 1, the carbon material is carbonized (step S1). Here, “carbonization treatment” means that an organic substance in the carbon material is decomposed by heating to be in a carbon-rich state. Examples of means for heating the carbon material include, but are not necessarily limited to, a combustion apparatus, a superheated steam baking apparatus, and an electric furnace.

(炭化材料の出発原料)
なお、炭素材料の出発原料として、廃コーヒー豆や籾殻、椰子殻等の植物由来の材料が挙げられるが、必ずしもこれらに限定されない。特に、籾殻や廃コーヒー豆は大量に排出される割にリサイクルが進んでいない産業廃棄物であるため、これらを有効利用することが望ましい。なお、籾殻は米の収穫によって排出される産業廃棄物である。日本における籾殻の年間排出量は約1300万トンと言われているが、この内の約30パーセントが土壌改質剤、肥料、暖房燃料として利用されているが、大半は廃棄されているのが現状である。
(Starting material of carbonized material)
Examples of the carbon material starting material include plant-derived materials such as waste coffee beans, rice husks, and coconut husks, but are not necessarily limited thereto. In particular, rice husks and waste coffee beans are industrial wastes that have not been recycled even though they are discharged in large quantities, so it is desirable to effectively use them. Rice husk is an industrial waste discharged by rice harvest. The annual emissions of rice husk in Japan is said to be about 13 million tons, of which about 30 percent is used as soil conditioner, fertilizer and heating fuel, but the majority is discarded. Currently.

なお、図2は、上述した炭化処理工程S1のうち特に好ましい態様を説明した図である。具体的には、図2(a)に特に好ましい態様の炭化処理工程S1のフローチャートを示し、図2(b)に工程S1で使用する燃焼装置1の一例を示し、図2(c)にこの燃焼装置1の回転式燃焼窯3を正面から観た図を示す。この特に好ましい炭化処理工程S1では、図2(a)〜(c)に示すように、出発原料としては籾殻を使用し、これを燃焼装置1のフィーダー2に投入する(工程S11)。その後、図2(c)に示すように、燃焼装置1の回転式燃焼窯3内で籾殻4aを回転させながら500℃〜600℃の温度で加熱(炭化)させる(工程S12)。ここで、回転式燃焼窯3内を籾殻4aが回転しながら通過する時間を30秒〜120秒(さらに好ましくは、60秒〜80秒)程度に設定することが好ましい。回転式燃焼窯3から燃焼装置1の外部へ排出された籾殻4bは、自然冷却させられながら回収容器5に回収される(工程S13、S14)。   In addition, FIG. 2 is a figure explaining the especially preferable aspect among carbonization process process S1 mentioned above. Specifically, FIG. 2 (a) shows a flowchart of a particularly preferred carbonization treatment step S1, FIG. 2 (b) shows an example of the combustion apparatus 1 used in step S1, and FIG. The figure which looked at the rotary combustion kiln 3 of the combustion apparatus 1 from the front is shown. In this particularly preferable carbonization treatment step S1, as shown in FIGS. 2 (a) to 2 (c), rice husk is used as a starting material, which is put into the feeder 2 of the combustion apparatus 1 (step S11). Then, as shown in FIG.2 (c), it heats (carbonizes) at the temperature of 500 to 600 degreeC, rotating the rice husk 4a within the rotary combustion kiln 3 of the combustion apparatus 1 (process S12). Here, it is preferable to set the time during which the rice husk 4a passes through the rotary combustion kiln 3 while rotating to about 30 seconds to 120 seconds (more preferably, 60 seconds to 80 seconds). The rice husk 4b discharged from the rotary combustion kiln 3 to the outside of the combustion apparatus 1 is recovered in the recovery container 5 while being naturally cooled (steps S13 and S14).

(アルカリ賦活処理)
次に、炭化処理工程S1により処理された炭素材料にアルカリ賦活を施す(工程S2)。なお、「賦活」とは一般に、炭素材料に細孔構造を発達させ多孔質化する処理のことを意味する。特に、「アルカリ賦活」とは、薬品賦活の一種であり、炭素材料にアルカリ金属化合物を添加し、これを不活性雰囲気中で500〜800℃で焼成し、微細孔を持つ多孔質炭素を作製する方法である。
(Alkaline activation treatment)
Next, alkali activation is performed on the carbon material treated in the carbonization treatment step S1 (step S2). “Activation” generally means a treatment for developing a porous structure of a carbon material to make it porous. In particular, “alkali activation” is a kind of chemical activation. An alkali metal compound is added to a carbon material, and this is baked at 500 to 800 ° C. in an inert atmosphere to produce porous carbon having fine pores. It is a method to do.

このアルカリ賦活処理工程S2では、触媒のアルカリ金属元素(例えば、カリウム(K))がC−C結合の壊裂・分解を引き起こすことによって炭素材料は多孔質化する。添加するアルカリ金属化合物には、水酸化カリウム(KOH)、水酸化ナトリウム(NaOH)、水酸化リチウム(LiOH)、炭酸カリウム(KCO)、炭酸ナトリウム(NaCO)が挙げられる。 In this alkali activation treatment step S2, the carbon material is made porous by causing the alkali metal element (for example, potassium (K)) of the catalyst to cause breakage / decomposition of the C—C bond. Examples of the alkali metal compound to be added include potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), potassium carbonate (K 2 CO 3 ), and sodium carbonate (Na 2 CO 3 ).

なお、KOHは、NaOHやLiOHに比べて触媒活性が高い点で好ましい。つまり、KOHは賦活プロセス中にカリウム(K)と水酸化物イオン(OH)とに分離し、直ちにカリウムKが炭素質のガス化反応の触媒として作用する。カリウムKは他のアルカリ金属と比較して、原子半径が大きく最外殻電子の束縛エネルギーが小さく、電気陰性度が低いため、ガス化反応の触媒としての能力が高い。また、植物由来の炭(炭素材料)にはカリウムKが本来数%以下程度含まれているので炭素材料との親和性の面からもKOHは好ましい。   In addition, KOH is preferable at a point with high catalyst activity compared with NaOH and LiOH. That is, KOH is separated into potassium (K) and hydroxide ions (OH) during the activation process, and potassium K immediately acts as a catalyst for the carbonaceous gasification reaction. Compared with other alkali metals, potassium K has a large atomic radius, a small binding energy of outermost electrons, and a low electronegativity, and therefore has high ability as a catalyst for gasification reaction. In addition, since plant-derived charcoal (carbon material) originally contains about several percent or less of potassium K, KOH is also preferred from the standpoint of affinity with the carbon material.

なお、図3は、上述したアルカリ賦活処理工程S2のうち特に好ましい態様を説明した図である。具体的には、図3(a)に特に好ましい態様の賦活工程S2のフローチャートを示し、図3(b)に工程S2で使用する賦活処理装置の一例を示し、図3(c)に賦活処理の際の昇温パターンを示す。図3(b)に示すように、炭化処理工程S1により炭化された炭素材料4bに、該炭素材料の重量比で1〜5倍量のアルカリ賦活剤11を添加し、ムライト製坩堝12に導入し、坩堝12の上部をセラミックスウール等の通気性蓋材13で覆うことで原料仕込みを行う(工程S21)。更に、炭素材料4bやアルカリ賦活剤11を含んだムライト製坩堝12を、このムライト製坩堝12の寸法より大きな内部空間を有するSiC製坩堝14に挿入した後、周囲を粒子炭15で覆った状態で図示しない電気炉にセットし、賦活工程を行う(工程S22)。ここで、工程S22は、図3(c)に示すように大気密閉状態で昇温速度8℃/min、850℃、2hの昇温条件で賦活を行うことが好ましい。その後、賦活された炭素材料4bを自然冷却させる(工程S23)。その後、炭素材料4bを洗浄した後、乾燥処理を行った後、回収する(工程S24及び工程S25)。   In addition, FIG. 3 is a figure explaining the especially preferable aspect among alkali activation treatment process S2 mentioned above. Specifically, FIG. 3 (a) shows a flowchart of the activation step S2 in a particularly preferable mode, FIG. 3 (b) shows an example of the activation processing device used in step S2, and FIG. 3 (c) shows the activation processing. The temperature rising pattern at the time of this is shown. As shown in FIG. 3B, the alkali activator 11 is added in an amount of 1 to 5 times the weight ratio of the carbon material to the carbon material 4b carbonized in the carbonization step S1, and introduced into the mullite crucible 12. Then, the raw material is charged by covering the upper part of the crucible 12 with a breathable lid member 13 such as ceramic wool (step S21). Furthermore, after inserting the mullite crucible 12 containing the carbon material 4b and the alkali activator 11 into the SiC crucible 14 having an internal space larger than the dimension of the mullite crucible 12, the surroundings are covered with the particulate carbon 15. Then, it is set in an electric furnace (not shown) and an activation process is performed (process S22). Here, as shown in FIG. 3 (c), the step S22 is preferably activated under the temperature rising conditions of a temperature rising rate of 8 ° C./min, 850 ° C., and 2 hours in an airtight state. Thereafter, the activated carbon material 4b is naturally cooled (step S23). Then, after washing | cleaning the carbon material 4b, it collects, after performing a drying process (process S24 and process S25).

(多段階賦活処理)
さらに、アルカリ賦活処理工程S2においては、炭化処理S1された一つの炭素材料4bに対して、異なる種類のアルカリ賦活剤(例えば、KOHとNaOH)を用いて多段階的にアルカリ賦活を施してもよい。これにより、各賦活剤の触媒活性等の違いから、孔径が異なる二種類以上の細孔を炭素材料4b内に形成することが可能になる。
(Multi-stage activation process)
Further, in the alkali activation treatment step S2, even if the carbon material 4b subjected to the carbonization treatment S1 is subjected to alkali activation in multiple stages using different types of alkali activation agents (for example, KOH and NaOH). Good. Thereby, it becomes possible to form two or more kinds of pores having different pore diameters in the carbon material 4b due to differences in the catalytic activity of the respective activators.

アルカリ金属化合物の添加量としては、炭素材料4bとの重量比で、好ましくは3〜8倍(さらに好ましくは約5倍)のアルカリ金属化合物を添加する。   The addition amount of the alkali metal compound is preferably 3 to 8 times (more preferably about 5 times) of the alkali metal compound in a weight ratio to the carbon material 4b.

具体的に説明すると、炭素材料4bは多数のグラフェンからなるグラファイト層が多数積層されているが、アルカリ賦活処理工程S2はグラファイト層間に細孔(特に、ミクロ孔)の形成を促進することになる。   More specifically, the carbon material 4b has a large number of graphite layers made of graphene, but the alkali activation treatment step S2 promotes the formation of pores (particularly, micropores) between the graphite layers. .

(多孔質炭素材料の収容及び水素の導入)
以上のように作製された多孔質炭素を耐圧容器内に収容する(工程S3)。次に、この容器内部を水素の液化温度(20.3K)よりも高い77〜150Kの範囲内の温度に保持しながら、高圧の水素を該容器内部に導入する(工程S4)。ここで、水素導入後の平衡状態圧力が0.5〜20MPa(好ましく2〜12MPa)になるように水素を導入する。平衡状態圧力が0.5MPaより低いと多孔質炭素のミクロ孔に水素分子が十分に凝集・吸蔵されず、一方20MPaより高いと、過圧状態となり、多孔質炭素内での凝集・吸蔵性能が生かされない。
(Housing of porous carbon material and introduction of hydrogen)
The porous carbon produced as described above is accommodated in a pressure resistant container (step S3). Next, high-pressure hydrogen is introduced into the container while maintaining the inside of the container at a temperature in the range of 77 to 150 K higher than the liquefaction temperature of hydrogen (20.3 K) (step S4). Here, hydrogen is introduced so that the equilibrium pressure after hydrogen introduction is 0.5 to 20 MPa (preferably 2 to 12 MPa). When the equilibrium pressure is lower than 0.5 MPa, hydrogen molecules are not sufficiently aggregated and occluded in the micropores of the porous carbon. On the other hand, when the pressure is higher than 20 MPa, an overpressure state occurs and the agglomeration and occlusion performance in the porous carbon is high. It is not alive.

なお、容器内部(すなわち、多孔質炭素と水素)の温度は、室温に近づいて高ければ高い程、多くの利点がある。すなわち、温度を維持するための電力が少なくて済むとともに、温度維持のための装置を小型化することが可能となり、貯蔵・輸送上の水素の取扱が容易となる。しかしながら、容器内の水素が、液化水素のように高い水素密度で多孔質炭素の細孔空間全体内に凝集されていなければならない。本発明者らの知見によれば、容器内の水素は液化温度に近い77〜150Kの温度に設定されていることが望ましく、これにより液化状態の水素密度に近い密度で吸蔵挙動を示すことが分かっている。   In addition, there are many advantages, so that the temperature inside a container (namely, porous carbon and hydrogen) is so high that it approaches room temperature. That is, less power is required to maintain the temperature, and it is possible to reduce the size of the apparatus for maintaining the temperature, which facilitates handling of hydrogen for storage and transportation. However, the hydrogen in the container must be aggregated in the entire pore space of the porous carbon with a high hydrogen density like liquefied hydrogen. According to the knowledge of the present inventors, it is desirable that the hydrogen in the container is set to a temperature of 77 to 150 K that is close to the liquefaction temperature, and accordingly, the storage behavior is exhibited at a density close to the hydrogen density in the liquefied state. I know.

以上説明した工程S1〜S4を実行することで、炭素材料4bから多孔質炭素を形成し、この多孔質層中の各細孔に水素を吸蔵することが可能になる。   By executing the steps S1 to S4 described above, porous carbon can be formed from the carbon material 4b, and hydrogen can be stored in each pore in the porous layer.

(多孔質炭素の細孔構造)
多孔質炭素の細孔直径d(以下、単に「細孔径」、「孔径」、又は「径」とも呼ぶ。)は、一般に、広い分布を持っており、IUPAC(International Union of Pure and Applied Chemistry、国際純正・応用化学連合)では表1に示すような分類がなされている(詳しくは、IUPAC, Manual Symbols and Termilogy, (1972)を参照。)。表1に示すように、「ミクロ孔」とは2nm以下の径dを有した孔のことであり、これより大きな孔は、メゾ孔(2〜50nmの径dを有した孔)やマクロ孔(50nm以上の径dを有した孔)と定義されている。
(Pore structure of porous carbon)
The pore diameter d p of porous carbon (hereinafter, also simply referred to as “pore diameter”, “pore diameter”, or “diameter”) generally has a wide distribution, and IUPAC (International Union of Pure and Applied Chemistry). In the International Union of Pure and Applied Chemistry, classification as shown in Table 1 is made (for details, see IUPAC, Manual Symbols and Termology, (1972)). As shown in Table 1, the term "micropore" is that the holes have the following diameters d p 2 nm, which larger pores, Ya Mezoana (holes having a diameter d p of 2 to 50 nm) is defined as macropores (pores having a diameter d p of more than 50 nm).

従来技術によれば、上述したように、水素吸蔵に適している多孔質炭素の細孔はdが2nm未満のミクロ孔であることが指摘されている。これは、ミクロ孔が、ガスや分子サイズの物質に対応した寸法であるため強い吸蔵力を発揮する水素吸蔵サイトになり、一方、ミクロ孔より大きなメゾ孔やマクロ孔は、多孔質炭素の外部からその最奥部のミクロ孔まで水素を案内するための導入通路と考えられているからである(非特許文献5)。 According to the prior art, as described above, the pores of the porous carbon suitable for hydrogen storage is has been pointed out that d p is the micropores of less than 2 nm. This is a hydrogen storage site that exerts a strong occlusion force because the micropores have dimensions corresponding to gas and molecular size substances, while mesopores and macropores larger than micropores are external to the porous carbon. This is because it is considered as an introduction passage for guiding hydrogen to the innermost micropore (Non-Patent Document 5).

本発明者らは、確かに、ミクロ孔は従来の上記知見のように水素吸蔵サイトとして有効であるが、従来、水素導入通路と考えられてきたメゾ孔が水素吸蔵サイトとして十分に機能することを発見した。そこで、本発明者らは、外部からの水素を、炭素中のミクロ孔のみならずメゾ孔にも吸蔵させることに適した多孔質炭素やこの多孔質炭素を用いて水素吸蔵させる方法を提供することを狙ったのである。   The present inventors have confirmed that micropores are effective as hydrogen storage sites as in the above-mentioned conventional knowledge, but that mesopores that have been conventionally considered as hydrogen introduction passages function sufficiently as hydrogen storage sites. I found Accordingly, the present inventors provide porous carbon suitable for storing external hydrogen not only into micropores in carbon but also into mesopores, and a method for storing hydrogen using this porous carbon. I aimed for that.

本発明の多孔質炭素の細孔構造や多孔質炭素への水素吸蔵量を特定するに当たっては、例えば、以下に説明するような測定法を実施することで評価することが可能である。   In specifying the pore structure of the porous carbon of the present invention and the hydrogen occlusion amount in the porous carbon, for example, it can be evaluated by carrying out a measurement method as described below.

(比表面積の測定法)
本発明の多孔質炭素の比表面積の測定は、窒素ガスなどの吸着によって得られた吸着等温線から解析を行うBET吸着法(Brunauer、Emmet、及びTellerによって理論的に導出された測定法)を利用している。このBET吸着法によって測定された比表面積を以下、「BET比表面積」と呼ぶ。
(Measurement method of specific surface area)
The measurement of the specific surface area of the porous carbon of the present invention is based on the BET adsorption method (measurement method theoretically derived by Brunauer, Emmet, and Teller) that analyzes from the adsorption isotherm obtained by adsorption of nitrogen gas or the like. We are using. Hereinafter, the specific surface area measured by the BET adsorption method is referred to as “BET specific surface area”.

(ミクロ孔の細孔径の測定法)
また、多孔質炭素内のミクロ孔の細孔径(ポアサイズ)測定には、Mikhailらによって提案されたMicro−pore法(MP法)を利用している。MP法では、まずBET吸着法により得られた単分子吸着量を用いて吸着層の厚みt(及び標準t−plot)が算出され、その後、細孔の表面積及び容積が算出されて、細孔径d(ポアサイズ)が導かれる。
(Measurement method of micropore diameter)
In addition, the micro-pore method (MP method) proposed by Mikhal et al. Is used to measure the pore size (pore size) of the micropores in the porous carbon. In the MP method, the thickness t (and standard t-plot) of the adsorption layer is first calculated using the monomolecular adsorption amount obtained by the BET adsorption method, and then the pore surface area and volume are calculated to obtain the pore diameter. d p (pore size) is derived.

(メゾ孔の細孔径の測定法)
また、多孔質炭素内のメゾ孔の細孔径測定には、BJH(Berret−Joyner−Halenda)法を利用している。BJH法では、孔形状が円筒状であると仮定し、窒素ガスの吸着等温線からKelvin式に基づいて細孔径dの分布を算出する方法である。
(Measuring method of mesopore diameter)
Moreover, the BJH (Berret-Joyner-Halenda) method is utilized for the measurement of the pore diameter of the mesopores in the porous carbon. The BJH method is a method for calculating the distribution of the pore diameter d p from the nitrogen gas adsorption isotherm based on the Kelvin equation, assuming that the pore shape is cylindrical.

(水素吸蔵量の測定法)
本発明の多孔質炭素の水素吸蔵量の測定には、容量法を利用している。容量法とは、一定体積の系内の水素量の変化を測定前後の圧力差、温度から求めるものである。具体的には、水素吸蔵合金の圧力−組成等温線(PCT線)を測定する方法(JIS H 7201)に準じて行われる方法であり、「ジーベルツ法」と呼ばれる。
(Measurement method of hydrogen storage amount)
For the measurement of the hydrogen storage capacity of the porous carbon of the present invention, the volume method is used. In the capacity method, the change in the amount of hydrogen in a system with a constant volume is obtained from the pressure difference and temperature before and after the measurement. Specifically, this is a method performed in accordance with a method (JIS H 7201) for measuring a pressure-composition isotherm (PCT line) of a hydrogen storage alloy, and is called “Sieberz method”.

以下に実施例を挙げて本発明をさらに具体的に説明するが、本発明はこれらの例に限定されるものではない。なお、以下の実施例においては、賦活処理工程前及び賦活工程中の炭素原料を「炭素材料」、賦活工程後の炭素原料を「多孔質炭素」、「活性炭」或いは「水素吸蔵材料」と称する。   EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following examples, the carbon raw material before and during the activation process is referred to as “carbon material”, and the carbon raw material after the activation process is referred to as “porous carbon”, “activated carbon”, or “hydrogen storage material”. .

表2に、本発明の実施例に係る多孔質炭素の作製条件の詳細を示す。実施例においては、炭素材料の出発原料として籾殻又は廃コーヒー豆を用い、表2に示すようにAC1乃至AC5と命名された5つの試料を用意した。   Table 2 shows details of conditions for producing porous carbon according to the examples of the present invention. In the examples, rice husks or waste coffee beans were used as starting materials for carbon materials, and five samples named AC1 to AC5 were prepared as shown in Table 2.

(実施例:炭化処理工程S1)
AC1乃至AC3の試料については、籾殻を出発原料として、図2で説明した工程S11〜S14を含む炭化処理S1を行った。なお、この処理を行う燃焼装置として、籾殻燻炭製造機(株式会社武井建設製)を用い、加熱温度を500℃〜600℃、試料AC1〜AC3が回転式燃焼窯内を通過する時間を70秒間に設定して試料を炭化した(上述の工程S11〜S14を参照)。
(Example: Carbonization treatment step S1)
The samples AC1 to AC3 were subjected to carbonization treatment S1 including steps S11 to S14 described with reference to FIG. 2 using rice husk as a starting material. In addition, as a combustion apparatus which performs this process, the rice husk charcoal making machine (made by Takei Construction Co., Ltd.) is used. The sample was carbonized by setting to seconds (see steps S11 to S14 described above).

なお、AC4の試料の炭化処理S1については、出発原料である廃コーヒー豆を乾燥処理した後にガス賦活の一種である水蒸気賦活を施すことにした。具体的には、廃コーヒー豆を恒温乾燥機中で120℃、24h(hは時間)乾燥処理した。通気性のあるステンレス製容器に試料AC4を挿入した後、直径1.0mm程度の竹炭粒子で周囲を覆った状態で過熱水蒸気発生装置(第一高周波工業製)内に設置した。まず、水蒸気流量45g/minの雰囲気下で500℃、1〜3hで炭化を行った後、水蒸気流量45g/min、COガス流量10l/minの雰囲気下で800℃、2hの水蒸気賦活を5回繰り返し行うことで炭素材料を調製した。 In addition, about carbonization process S1 of the sample of AC4, it decided to give the steam activation which is a kind of gas activation after drying the waste coffee bean which is a starting material. Specifically, waste coffee beans were dried in a constant temperature dryer at 120 ° C. for 24 hours (h is time). After the sample AC4 was inserted into a breathable stainless steel container, the sample AC4 was placed in a superheated steam generator (Daiichi Kogyo Kogyo Co., Ltd.) in a state of being covered with bamboo charcoal particles having a diameter of about 1.0 mm. First, carbonization was performed at 500 ° C. for 1 to 3 hours in an atmosphere with a steam flow rate of 45 g / min, and then steam activation at 800 ° C. for 2 hours in an atmosphere with a steam flow rate of 45 g / min and a CO 2 gas flow rate of 10 l / min was performed. The carbon material was prepared by repeating the process once.

また、AC5の試料については、既に炭化処理されている市販の籾殻を購入した。   Moreover, about the sample of AC5, the commercial rice husk already carbonized was purchased.

(実施例:アルカリ賦活工程S2)
炭化処理工程S1により炭化及び調製された炭素材料(試料AC1〜AC5)にアルカリ賦活剤として水酸化カリウム(ナカライテスク製:KOH)を添加し、熱処理によって多孔質炭素を調製した(上述の工程S21〜S24を参照)。まず、炭素材料5.0gに該炭素材料の重量比で1〜5倍量のKOHを添加した後(表2を参照)、ムライト製ルツボに導入し、上部をセラミックスウールで覆った。更に、SiC製坩堝に挿入した後、周囲を粒子炭で覆った状態で電気炉にセットし、大気密閉状態で昇温速度8℃/min、850℃、2hの条件でアルカリ賦活処理S2を行った。アルカリ賦活工程S2後、蒸留水による洗浄を行った後、恒温乾燥機中で100℃、24hの条件で乾燥処理して多孔質炭素を得た。
(Example: Alkaline activation step S2)
Potassium hydroxide (manufactured by Nacalai Tesque: KOH) was added as an alkali activator to the carbon material (samples AC1 to AC5) carbonized and prepared in the carbonization treatment step S1, and porous carbon was prepared by heat treatment (the above-described step S21). To S24). First, 1 to 5 times the amount of KOH by weight ratio of the carbon material was added to 5.0 g of the carbon material (see Table 2), and then introduced into a mullite crucible, and the upper portion was covered with ceramic wool. Further, after being inserted into a SiC crucible, it was set in an electric furnace with the surroundings covered with particulate charcoal, and an alkali activation treatment S2 was performed under conditions of a temperature rising rate of 8 ° C./min, 850 ° C., and 2 hours in an airtight state. It was. After performing the alkali activation step S2, washing with distilled water was performed, followed by drying at 100 ° C. for 24 hours in a constant temperature dryer to obtain porous carbon.

なお、表3にアルカリ賦活工程S2を施した後の多孔質炭素の細孔構造を上述の測定手法によって評価した結果を示す。この表3から明らかなように、上述の炭化処理工程S1及びアルカリ賦活処理工程S2の条件を変化させることにより、比表面積、ミクロ孔容積、メゾ孔容積、平均細孔直径などが異なる活性炭(多孔質炭素)を合成(作製)できることが分かる。   In addition, the result of having evaluated the pore structure of the porous carbon after performing alkali activation process S2 with the above-mentioned measuring method in Table 3 is shown. As is apparent from Table 3, activated carbon (porous) having different specific surface area, micropore volume, mesopore volume, average pore diameter, etc., by changing the conditions of the carbonization treatment step S1 and the alkali activation treatment step S2 described above. It can be seen that carbon can be synthesized (produced).

(多孔質炭素のミクロ孔の細孔径分布)
図4(a)に、上記試料AC1〜AC3において、MP法から算出したミクロ孔の細孔径分布と細孔容積を示す。図4(a)の横軸には細孔径d(単位:nm)を示し、縦軸には細孔径dの微小変化d(d)に対応した細孔容積Vの変化量dVを示している。この結果から、KOHの添加量が1倍と少ない試料AC1においても、0.6nm付近の細孔径dを有したミクロ孔が形成されていることが分かる。さらに、試料AC2、AC3の結果より、KOHの添加量を3倍、5倍と増加させるに従って、0.6nmの径のミクロ孔以外にも、0.6nmより大きな径(例えば、1.0nm、1.2nm、1.5nm)の細孔が形成されていることが分かる。KOHの添加量の増加により、賦活量が増加し、その結果として、ミクロ孔自体の孔径dの拡大やミクロ孔同士の連結が起こっていると考えられる。
(Porosity distribution of micropores in porous carbon)
FIG. 4A shows the pore size distribution and pore volume of the micropores calculated from the MP method in the samples AC1 to AC3. FIGS. 4 (a) pore size d p (unit: nm) in the horizontal axis shows the amount of change in pore volume V corresponding to minute changes d (d p) of pore diameter d p and the vertical axis dV p Is shown. From this result, even in the amount of 1-fold and less sample AC1 of KOH, it is understood that the micropores having a pore diameter d p of around 0.6nm is formed. Further, from the results of the samples AC2 and AC3, as the amount of KOH added is increased 3 times and 5 times, in addition to the micropores having a diameter of 0.6 nm, a diameter larger than 0.6 nm (for example, 1.0 nm, It can be seen that 1.2 nm and 1.5 nm) pores are formed. By increasing the amount of KOH, activated volume increases, as a result, it is considered that coupling of the expansion and micropores between the pore diameter d p of the micropores themselves going.

図4(b)に、上記試料AC3〜AC5において、MP法から算出したミクロ孔の細孔径分布と細孔容積を示す。これらの試料AC3〜AC5は、出発原料の種類と炭化処理S1での処理方法が上述のように異なっているが、アルカリ賦活処理工程S2でのKOHの添加量についてはどの試料も5倍である。   FIG. 4B shows the pore size distribution and pore volume of the micropores calculated from the MP method in the samples AC3 to AC5. These samples AC3 to AC5 are different in the type of starting material and the treatment method in the carbonization treatment S1 as described above, but the amount of KOH added in the alkali activation treatment step S2 is five times as large as any sample. .

図4(b)に示すように、試料AC4,試料AC5も試料AC3と同様に、0.6nmの孔径dの他、これより大きなサイズの1.0nm〜1.2nmの程度の孔径dで顕著な細孔容積が確認される。特に試料AC3の場合は、メゾ孔との境界値である2nmまでミクロ孔の発達が確認される。従って、5倍量のKOHの添加によって、多孔質炭素内により広い孔径分布を有したミクロ孔が発達することが分かった。 FIG 4 (b) as shown in, the similar sample AC4, sample AC5 also sample AC3, other pore diameter d p of 0.6 nm, which from the large degree of 1.0nm~1.2nm pore diameter d p A marked pore volume is confirmed. In particular, in the case of sample AC3, the development of micropores is confirmed up to 2 nm, which is the boundary value with mesopores. Therefore, it was found that by adding 5 times the amount of KOH, micropores having a wider pore size distribution were developed in the porous carbon.

(多孔質炭素のメゾ孔の細孔径分布)
図5(a)に、上記試料AC1〜AC3において、BJH法から算出したメゾ孔の細孔径分布と細孔容積を示す。図5(a)の横軸及び縦軸の表示方法は上述の図1、2の表示方法と同様である。この図5(a)の結果から、孔径dが2nm〜10nmの範囲のメゾ孔が試料AC1〜AC3中の多孔質層に形成・発達していること及びKOHの添加量の増加に従い、より大きな孔径dのメゾ孔の発達(これに対応した容積の増加)が確認される。
(Pore diameter distribution of mesopores in porous carbon)
FIG. 5A shows the pore size distribution and pore volume of mesopores calculated from the BJH method in the samples AC1 to AC3. The display method of the horizontal and vertical axes in FIG. 5A is the same as the display method of FIGS. The results of this FIG. 5 (a), the with increasing that mesopores ranging pore diameter d p is 2nm~10nm forms and development on the porous layer in the sample AC1~AC3 and amount of KOH, more large pore size d p development of mesopores in (increase in volume corresponding thereto) is confirmed.

図5(b)に、上記試料AC3〜AC5において、BJH法から算出したメゾ孔の細孔径分布と細孔容積を示す。図5(b)に示すように、試料AC4,試料AC5でも試料AC3と同様に、孔径dが2nm〜10nmの範囲のメゾ孔の発達が確認されるが、試料AC3の場合と比較して顕著ではない。 FIG. 5B shows the pore size distribution and pore volume of mesopores calculated from the BJH method in the samples AC3 to AC5. As shown in FIG. 5 (b), sample AC4 and sample AC5 also show mesopore development in the range of 2 nm to 10 nm in pore diameter d p as in sample AC3, but compared to sample AC3. Not noticeable.

(ミクロ孔とメゾ孔との容積比)
上述したように、試料AC1〜AC5においては、メゾ孔発達の程度が異なっていた為、ミクロ孔の容積に対するメゾ孔の容積の割合を算出してみた(以下の数式を参照)。これらの結果は表3に示されている。表3の結果によれば、試料AC1〜AC3の場合は比較的高い容積比を有し、特にAC3の場合は0.866とミクロ孔とほぼ同等の容積量を有する。一方、試料AC4やAC5の場合は、試料AC3と同じKOH添加量を与えて作製されているが、試料AC3の場合のような高い容積比は得られていない。これは、出発原料の種類や炭化処理工程S1の処理方法の違いが細孔構造の形成に影響を与えていると考えられる。
(Volume ratio between micropores and mesopores)
As described above, in the samples AC1 to AC5, since the degree of mesopore development was different, the ratio of the mesopore volume to the micropore volume was calculated (see the following formula). These results are shown in Table 3. According to the results in Table 3, the samples AC1 to AC3 have a relatively high volume ratio, and in particular, the case of AC3 has a volume amount of 0.866, which is almost equivalent to a micropore. On the other hand, the samples AC4 and AC5 are produced by giving the same KOH addition amount as the sample AC3, but a high volume ratio as in the case of the sample AC3 is not obtained. This is thought to be due to the difference in the type of starting material and the treatment method of the carbonization treatment step S1 affecting the formation of the pore structure.

(水素吸蔵特性評価)
以上のようにして作製された多孔質炭素の水素吸蔵特性を上記ジーベルツ法により評価した。図6に水素吸蔵特性評価装置の概略を示す。多孔質炭素(試料AC1〜AC5)を約0.1〜0.5g充填した容器をマントルヒーターにより150℃に加熱し、ターボ分子ポンプとロータリーポンプにより1.0×10−3Paの減圧下にて1hの脱ガス処理を行った。脱ガス処理後、容器を恒温槽(液体窒素を満たしたデュワー瓶)に浸漬させ多孔質炭素を77Kに7分間保持した。
(Hydrogen storage characteristics evaluation)
The hydrogen storage characteristics of the porous carbon produced as described above were evaluated by the Siebelz method. FIG. 6 shows an outline of an apparatus for evaluating hydrogen storage characteristics. A container filled with about 0.1 to 0.5 g of porous carbon (samples AC1 to AC5) is heated to 150 ° C. by a mantle heater, and reduced to 1.0 × 10 −3 Pa by a turbo molecular pump and a rotary pump. For 1 h. After the degassing treatment, the container was immersed in a thermostatic bath (Dewar bottle filled with liquid nitrogen) to hold the porous carbon at 77K for 7 minutes.

水素吸蔵量の測定は、図6の導入バルブVを開放して導入バルブVを閉鎖し、水素導入室に水素を導入する。水素導入室の圧力が一定になったら導入バルブVを解放して容器に水素を導入し、水素導入室と容器の圧力変化を測定した。水素導入室および容器の平衡圧力を0.5MPaから10.0MPaへと導入圧力を段階的に加圧することで吸蔵特性を測定し、さらに10.0MPaから0.5MPaへと導入圧力を段階的に減圧し、放出特性を測定することで水素吸蔵量を評価した。得られた水素吸蔵量から、Zuttelらの水素吸着理論式を用いて水素密度を算出した。 Measurement of hydrogen storage capacity is to open the inlet valve V 1 of the Figure 6 closes the inlet valve V 2, introducing hydrogen to the hydrogen supply chamber. Hydrogen was introduced to the vessel pressure of the hydrogen introducing chamber releases the inlet valve V 2 When became constant was measured pressure changes of the hydrogen supply chamber and the container. The storage pressure is measured by gradually increasing the introduction pressure from 0.5 MPa to 10.0 MPa in the equilibrium pressure of the hydrogen introduction chamber and the vessel, and the introduction pressure is gradually increased from 10.0 MPa to 0.5 MPa. The amount of hydrogen occlusion was evaluated by reducing the pressure and measuring the release characteristics. From the obtained hydrogen storage amount, the hydrogen density was calculated using the hydrogen adsorption theoretical formula of Zuttel et al.

(水素吸蔵特性結果)
図7(a)は試料AC1〜AC3に係る水素吸蔵特性を示し、一方、図7(b)は試料AC3〜AC5に係る水素吸蔵特性を示した図である。なお、各図の横軸は水素導入時の平衡圧力(単位はMPa)であり、縦軸は水素吸蔵量(単位はwt.%(重量パーセント))である。
(Results of hydrogen storage characteristics)
FIG. 7A shows the hydrogen storage characteristics of samples AC1 to AC3, while FIG. 7B shows the hydrogen storage characteristics of samples AC3 to AC5. In each figure, the horizontal axis represents the equilibrium pressure at the time of hydrogen introduction (unit: MPa), and the vertical axis represents the hydrogen storage amount (unit: wt.% (Weight percent)).

図7(a)の結果によれば、試料AC1や試料AC2の場合は、平衡圧力の増加とともに水素吸蔵量も急激に増加するが、ある圧力で最大となり、その後ほぼ一定あるいは若干低下することが確認される。具体的には、試料AC1の場合は約2MPaで最大水素吸蔵量が0.89wt.%を観測し、試料AC2の場合は約3MPaで最大水素吸蔵量が3.98wt.%を観測した。これに対して、試料AC3の場合は、この平衡圧力の範囲(0.5MPa〜10.0MPa)内では、平衡圧力の増加とともに水素吸蔵量も増加し続け、約10MPaの圧力下にて、最大水素吸蔵量が9.0wt.%を観測した。   According to the results shown in FIG. 7A, in the case of the sample AC1 or the sample AC2, the hydrogen storage amount increases rapidly with the increase of the equilibrium pressure, but becomes maximum at a certain pressure, and thereafter becomes almost constant or slightly decreased. It is confirmed. Specifically, in the case of the sample AC1, the maximum hydrogen storage amount is 0.89 wt. %, In the case of sample AC2, the maximum hydrogen occlusion amount is 3.98 wt. % Was observed. On the other hand, in the case of the sample AC3, within this equilibrium pressure range (0.5 MPa to 10.0 MPa), the hydrogen occlusion amount continues to increase as the equilibrium pressure increases. Hydrogen storage amount is 9.0 wt. % Was observed.

また、図7(b)の結果によれば、試料AC4や試料AC5の場合は、平衡圧力の増加とともに水素吸蔵量も急激に増加するが、ある圧力で最大となり、その後ほぼ一定あるいは若干低下することが確認される。具体的には、試料AC4の場合は約2MPaで最大水素吸蔵量が3.35重量パーセント(wt.%)を観測し、試料AC5の場合は約3.47MPaで最大水素吸蔵量が4.80wt.%を観測した。以上の結果をまとめたものが、以下の表4である。   Further, according to the result of FIG. 7B, in the case of the sample AC4 or the sample AC5, the hydrogen occlusion amount increases rapidly with the increase of the equilibrium pressure, but becomes maximum at a certain pressure, and thereafter becomes almost constant or slightly lower. That is confirmed. Specifically, in the case of the sample AC4, a maximum hydrogen storage amount of 3.35 weight percent (wt.%) Is observed at about 2 MPa, and in the case of the sample AC5, the maximum hydrogen storage amount is 4.80 wt. . % Was observed. Table 4 below summarizes the above results.

なお、いずれの試料AC1〜AC5の結果においても、平衡圧力を低圧から高圧に増加させた場合と高圧から低圧に減少させた場合との間に若干のヒステリシスを確認されたが、どちらの方向から変化させても同様のプロファイルを確認した。   In any of the samples AC1 to AC5, a slight hysteresis was observed between when the equilibrium pressure was increased from low pressure to high pressure and when the equilibrium pressure was decreased from high pressure to low pressure. The same profile was confirmed even if it was changed.

(比表面積と水素吸蔵量との関係)
上述の表3の測定結果と表4の測定結果とから、BET比表面積と最大水素吸蔵量との対応関係が明らかになり、この関係を図8に示す。なお、BET比表面積の測定には、高精度ガス/蒸気吸着測定装置(日本ベル株式会社製(装置名:BELSORP‐max1‐SPNG)を使用した。図8の結果から、多孔質炭素の最大水素吸蔵量は、BET比表面積の増加とともに指数関数的に増大することが確認される。比表面積と水素吸蔵量との対応関係が更に高いBET比表面積でも維持されると仮定した場合、BET比表面積3000m/g以上の多孔質炭素を形成できれば、15wt.%の水素吸蔵量が達成できることが見込まれる。
(Relationship between specific surface area and hydrogen storage capacity)
The correspondence between the BET specific surface area and the maximum hydrogen storage amount is clarified from the measurement results in Table 3 and Table 4, and this relationship is shown in FIG. For the measurement of the BET specific surface area, a high-precision gas / vapor adsorption measuring device (manufactured by Nippon Bell Co., Ltd. (device name: BELSORP-max1-SPNG) was used. From the results of FIG. It is confirmed that the amount of occlusion increases exponentially as the BET specific surface area increases, assuming that the correspondence between the specific surface area and the hydrogen occlusion amount is maintained even at a higher BET specific surface area. If porous carbon of 3000 m 2 / g or more can be formed, it is expected that a hydrogen storage amount of 15 wt.% Can be achieved.

(水素吸蔵密度)
従来の考え方を基に、水素が多孔質炭素中のミクロ孔のみに全て吸蔵されたと仮定して、Zuttelらによって提案された理論式により水素吸蔵密度を算出した。なお、理論式の詳細は、Zuttel et al., Appl. Phys. A 78 (2004) p.941を参照されたい。上述の表4に水素吸蔵密度の結果も示す。ところで、液体水素の理想的な密度は70.8mg/cmである。試料AC3の場合に算出された水素吸蔵密度は、上記理想値の約2倍に相当する145mg/cmを示した。
(Hydrogen storage density)
Based on the conventional concept, the hydrogen storage density was calculated by the theoretical formula proposed by Zuttel et al., Assuming that all the hydrogen was stored only in the micropores in the porous carbon. For details of the theoretical formula, see Zuttel et al. , Appl. Phys. A 78 (2004) p. 941. Table 4 above also shows the results of the hydrogen storage density. By the way, the ideal density of liquid hydrogen is 70.8 mg / cm 3 . The hydrogen storage density calculated in the case of sample AC3 was 145 mg / cm 3 corresponding to about twice the ideal value.

(ミクロ孔容積と水素吸蔵量との関係)
図9は、図8に使用したBET比表面積に代えてミクロ孔容積を横軸に取り、縦軸にその最大水素吸蔵量を示す。この図9に示すように、多孔質炭素の最大水素吸蔵量は、ミクロ孔容積の増加とともに増大することが分かる。加えて、ミクロ孔容積が約1.2(cm/g)程度までは直線的に増加しているが、ミクロ孔容積がこれより大きくなると急激に水素吸蔵量が増大していることが分かる(例えば、ミクロ孔容積が約1.81(cm/g)では最大水素吸蔵量が9.0wt.%である。)。この結果は、ミクロ孔容積以外の構造パラメータが影響を及ぼしていることを示唆している。
(Relationship between micropore volume and hydrogen storage capacity)
FIG. 9 shows the micropore volume on the horizontal axis instead of the BET specific surface area used in FIG. 8, and the maximum hydrogen storage amount on the vertical axis. As shown in FIG. 9, it can be seen that the maximum hydrogen storage capacity of the porous carbon increases as the micropore volume increases. In addition, the micropore volume increases linearly up to about 1.2 (cm 3 / g), but it can be seen that as the micropore volume becomes larger than this, the hydrogen storage amount suddenly increases. (For example, when the micropore volume is about 1.81 (cm 3 / g), the maximum hydrogen storage amount is 9.0 wt.%). This result suggests that structural parameters other than the micropore volume have an effect.

(ミクロ孔容積と水素吸蔵密度との関係)
図10(a)は、ミクロ孔容積(表3を参照)と水素吸蔵密度(表4を参照)との関係を示す。ここで、図中に示した横軸に対して平行な破線は、液体水素の理想的な密度の値(70.8mg/cm)を示す(後述の図10(b)及び図11の破線表示も同様である。)。図9の結果と同様に、ミクロ孔容積の増加に伴って、水素吸蔵密度も増加する傾向を示した。ミクロ孔容積約1.2(cm/g)から急激に水素吸蔵密度が増大した。ミクロ孔よりも大きな細孔(メゾ孔、マクロ孔)にも水素が吸蔵されている可能性が示唆される。
(Relationship between micropore volume and hydrogen storage density)
FIG. 10A shows the relationship between the micropore volume (see Table 3) and the hydrogen storage density (see Table 4). Here, the broken line parallel to the horizontal axis shown in the figure indicates the ideal density value (70.8 mg / cm 3 ) of liquid hydrogen (the broken line in FIG. 10B and FIG. 11 described later). The display is similar.) Similar to the results of FIG. 9, the hydrogen storage density tended to increase with increasing micropore volume. The hydrogen storage density rapidly increased from a micropore volume of about 1.2 (cm 3 / g). It is suggested that hydrogen may be occluded in pores larger than micropores (mesopores and macropores).

(メゾ孔容積と水素吸蔵密度との関係)
次に、メゾ孔容積と水素吸蔵密度との比較を行った。図10(b)は、メゾ孔容積(表3を参照)と水素吸蔵密度(表4を参照)との関係を示す。多孔質炭素のメゾ孔容積の増加に伴って、水素吸蔵密度も増加する傾向が確認された。
(Relationship between mesopore volume and hydrogen storage density)
Next, the mesopore volume and the hydrogen storage density were compared. FIG. 10B shows the relationship between the mesopore volume (see Table 3) and the hydrogen storage density (see Table 4). As the mesopore volume of porous carbon increased, the hydrogen storage density tended to increase.

(容積比と水素吸蔵密度との関係)
図11は、ミクロ孔容積に対するメゾ孔容積の容積比(表3及び数1を参照)と水素吸蔵密度(表4を参照)との関係を示す。この容積比の増加に伴って、水素吸蔵密度も増加する傾向が確認された。つまり、ミクロ孔容積に対してメゾ孔容積の比率が大きくなると、水素吸蔵量も増大することが示された。特に、容積比が0.5以上(特に、0.86以上)になると著しく高い水素吸蔵量が得られることが分かる。この結果から、ミクロ孔にのみならずメゾ孔にも気化状態の水素が吸蔵しており、メゾ孔も水素吸蔵サイトとして有望であることが示唆される。
(Relationship between volume ratio and hydrogen storage density)
FIG. 11 shows the relationship between the volume ratio of the mesopore volume to the micropore volume (see Table 3 and Equation 1) and the hydrogen storage density (see Table 4). As the volume ratio increased, the hydrogen storage density tended to increase. That is, it was shown that as the ratio of the mesopore volume to the micropore volume increases, the hydrogen storage amount also increases. In particular, it can be seen that when the volume ratio is 0.5 or more (particularly 0.86 or more), a significantly high hydrogen storage amount can be obtained. This result suggests that vaporized hydrogen is stored not only in micropores but also in mesopores, and that mesopores are also promising as hydrogen storage sites.

本発明は、燃料電池自動車の高性能化、これに関連する水素の製造、貯蔵、輸送技術に貢献できるものと考えられる。なお、本発明の水素吸蔵方法は、現時点において本発明者らが先に特許文献1にて提案した水素吸蔵方法よりも更に高い水素吸蔵特性を提供できることを実証している。   The present invention is considered to contribute to the enhancement of the performance of fuel cell vehicles and the related hydrogen production, storage, and transportation technologies. Note that the hydrogen storage method of the present invention has proved that it can provide higher hydrogen storage characteristics than the hydrogen storage method previously proposed by the present inventors in Patent Document 1 at the present time.

また、近年、水素を液化状態で貯蔵する水素ステーション構想が提唱されているが、絶対温度20.3Kの下で水素を冷却・管理する必要があること、液化水素から発生する水素ガスを一時的に貯蔵しておくバッファーのような装置が必要とされることが課題として挙げられている。本発明を上記技術構想に適用すれば、必ずしも水素温度を液化温度に設定しなくてもよく(より室温に近付けた温度に設定すればよく)、水素貯蔵用のバッファー装置もより実現し易くなるものと考えられる。   In recent years, a hydrogen station concept for storing hydrogen in a liquefied state has been proposed. However, it is necessary to cool and manage hydrogen under an absolute temperature of 20.3 K, and hydrogen gas generated from liquefied hydrogen is temporarily stored. The problem is that a device such as a buffer to be stored is required. If the present invention is applied to the above technical concept, the hydrogen temperature does not necessarily have to be set to the liquefaction temperature (it may be set to a temperature closer to room temperature), and a buffer device for storing hydrogen can be easily realized. It is considered a thing.

以上のように、本発明は産業上の利用可能性が非常に高い。   As described above, the present invention has very high industrial applicability.

S1 炭素材料に炭化を施す工程
S2 炭素材料にアルカリ賦活を施す工程
S3 多孔質炭素を容器内に収容する工程
S4 水素を容器内部に導入する工程
細孔の直径
S1 Step of carbonizing carbon material S2 Step of applying alkali activation to carbon material S3 Step of containing porous carbon in vessel S4 Step of introducing hydrogen into vessel d Diameter of p pore

Claims (8)

炭素材料に炭化を施す工程と、
前記炭化工程により処理された前記炭素材料にアルカリ賦活を施す工程と、
前記アルカリ賦活工程により作製された多孔質炭素を容器内に収容する工程と、
前記容器内部を77K〜150Kの範囲内の温度に保持しながら、平衡状態圧力が0.5MPa〜20MPaになるように水素を該容器内部に導入する工程と、を含み、かつ、
前記多孔質炭素として、複数のミクロ孔と複数のメゾ孔とを含み、前記多孔質炭素の全体の比表面積が700m/g〜3800m/gであり、かつ、該メゾ孔は、2nm〜10nmの範囲の孔径を有する多孔質炭素を使用することを特徴とする水素吸蔵方法。
A step of carbonizing the carbon material;
Applying alkali activation to the carbon material treated by the carbonization step;
Storing the porous carbon produced by the alkali activation step in a container;
Introducing hydrogen into the container so that the equilibrium pressure is 0.5 MPa to 20 MPa while maintaining the inside of the container at a temperature in the range of 77 K to 150 K, and
Examples porous carbon, and a plurality of micropores and a plurality of mesopores, the total specific surface area of the porous carbon is 700m 2 / g~3800m 2 / g, and the meso pores, 2 nm to A method for storing hydrogen, characterized by using porous carbon having a pore size in the range of 10 nm.
前記炭化工程では、前記炭素材料に籾殻を使用し、かつ、前記炭素材料を燃焼窯内で回転させながら加熱する工程を含むことを特徴とする請求項1に記載の水素吸蔵方法。   The hydrogen storage method according to claim 1, wherein the carbonizing step includes a step of using rice husk as the carbon material and heating the carbon material while rotating in a combustion kiln. 前記アルカリ賦活工程では、前記炭素材料との重量比で3倍〜8倍のアルカリ賦活剤を添加することを特徴とする請求項1又は2に記載の水素吸蔵方法。   3. The hydrogen storage method according to claim 1, wherein in the alkali activation step, an alkali activator having a weight ratio of 3 to 8 times with the carbon material is added. 前記アルカリ賦活剤として、水酸化カリウム、水酸化ナトリウム、水酸化リチウム、炭酸カリウム、炭酸ナトリウムの少なくとも1つを使用することを特徴とする請求項3に記載の水素吸蔵方法。   The hydrogen storage method according to claim 3, wherein at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium carbonate, and sodium carbonate is used as the alkali activator. 前記アルカリ賦活工程では、前記アルカリ賦活剤を使用して賦活工程を行った後に、先の前記賦活工程の該アルカリ賦活剤と異なる種類の前記アルカリ賦活剤を使用して賦活工程を複数回行うことを特徴とする請求項3又は4に記載の水素吸蔵方法。   In the alkali activation step, after the activation step is performed using the alkali activation agent, the activation step is performed a plurality of times using the alkali activation agent of a different type from the alkali activation agent in the previous activation step. The hydrogen storage method according to claim 3 or 4, wherein: 前記多孔質炭素として、前記ミクロ孔が占めるミクロ孔容積に対して前記メゾ孔が占めるメゾ孔容積の比率が0.5以上になる多孔質炭素を使用することを特徴とする請求項1〜5のいずれかに記載の水素吸蔵方法。   6. The porous carbon having a ratio of a mesopore volume occupied by the mesopore to a micropore volume occupied by the micropore is 0.5 or more as the porous carbon. The hydrogen storage method according to any one of the above. 複数のミクロ孔と複数のメゾ孔とを含んだ多孔質炭素からなり、
前記多孔質炭素の全体の比表面積が700m/g〜3800m/gであり、かつ、
該メゾ孔は、2nm〜10nmの範囲の孔径を有することを特徴とする水素吸蔵材料。
It consists of porous carbon containing multiple micropores and multiple mesopores,
The total specific surface area of the porous carbon is 700m 2 / g~3800m 2 / g, and,
The mesopores have a pore diameter in the range of 2 nm to 10 nm.
前記多孔質炭素は籾殻を炭化処理した後にアルカリ賦活処理を施したものであり、かつ、
前記ミクロ孔が占めるミクロ孔容積に対して前記メゾ孔が占めるメゾ孔容積の比率が0.5以上に設定されたものであることを特徴とする請求項7に記載の水素吸蔵材料。
The porous carbon has been subjected to an alkali activation treatment after carbonizing the rice husk, and
The hydrogen storage material according to claim 7, wherein a ratio of a mesopore volume occupied by the mesopores to a micropore volume occupied by the micropores is set to 0.5 or more.
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